hooper



Sept. 10, 1963 B. E. HooPER 3,103,611

SIGNALLING SYSTEM Filed Jan. 7, 1958 Sept. 10, 1963 5.12. HooPERSIGNALLING SYSTEM 5 Sheets-Sheet 2 Filed Jan. 7, 1958 United StatesPatent O 3,103,611 SIGNALLING SYSTEM Brian E. Hooper, Sherman Oaks,Calif., assigner to Packard-Bell Electronics Corporation, Los Angeles,Calif., a corporation of California Filed Jan. 7, 1958, Ser. No. 707,603

12 Claims. (Cl. 317-147) This invention relates to apparatus forremotely controlling the operation of a distant mechanism. Moreparticularly, the invention relates to apparatus for ytransmittingsignals in a particular code from an auto-mobile toward a `garage andtor receiving the signals at the lgarage tocontrol the opening andclos-ing of a door in the zgarage.

In this advancing age of automation, equipment is constantly beinginvented and developed -to simplify ,the tasks of men and women. lForexample, apparatus is now being used to transmit signals from anautomobile as the automobile approaches a garage so that the garage doorcan be opened without any necessity for the driver to -get out of thecar. Similarly, the apparatus can be operated to close a garage door,after the automobile has left the garage. This apparatus has beenespecially desirable in inclement or cold weather and has beenparticularly useful to Women drivers at night.

Remote control equipment for operating `garage doors has been steadilyincreasing in popularity. This increase in popularity has presentedcertain problems. One probh lem 'has resulted from thefact that all otthe manufacturers are allowed only a few transmitting frequencies bygovernmental authorities such as the Federal Communications Commission.When a number of different installations are made by dierentmanufacturers in a particular area, it may sometimes occur that a car approaching a particulary garage may open the door for that garage as wellas the door for other garages near the particular garage. This mayresult from Ithe fact that the particular garage may have aninstallation of one manfacturer, while other garages in the area mayhave an installation of other manufacturers. For this reason, it hasbecome necessary to dierentiate between installations in a neighborhoodeven though such dfilierent-iation has been made diicult by the use of asingle carrier frequency Itor the transmitted Isignal-s.

Various attempts have been made to :encode the carrier signals withindividual and particular platterns to distinguish each installationfrom the others. These attempts have not been entirely successful ir'roman operational standpoint since each gavage mstallation has not beenentirely independent in operation from all of the other garbageinstallations in the neighborhood. Furthermore, the equipment resulting'om such attempts has been eX- pensive .in spite oct the incompletesuccess from an openational standpoint. This invention provides a systemtor overcoming the above disadvantages and at the same time providingequipment of reduced cost.

Dhe system constituting this invention produces 'a carrier signal lofthe frequency specified by the governmental authorities. This carrier`signal is alternately modulated on a time-sharing basis by signals ot arelatively low frequency rand second signals of a relatively highfrequency. Each of the low frequencies and high frequencies can beadjusted for different installations to provide a differentiationbetween the installations.

For example, one installation may use signals ot 9 kilocycles per secondto constitute the llow frequency and signals of 29 kilocycles per secondto constitute the high frequency. Another installation may respectivelyuse signals of 11.5 .and 34 kilocycles per second as the low and highfrequencies. Similarly, a sthird installation may 3,103,611 PatentedSept. 1G, 1963 ICC 2 use modulating signals of 49 and 34 kilocycles persecond on `a timesharing basis. By using circuit-s tuned to theparticular trequenciea each installation is able to pass only signals atthe particular trequencies selected for that installation. The system isso designed that thel garage door can be opened only when the modulatingsignals at both the low and high frequencies are able to pass the tunedcircuits lat the installation. p

The system constituting this invention utilizes novel techniques tosimplify the construction of the system. For example, substantially thesame circuitry is used at the transmitter of an automobile to producethe modulating signals of relatively low irequency and the modulatingsignals of relatively high frequency on a time-sharing basis. At thereceiver, novel circuitry is used to actuate the garage door mechanismonly when both modulating ,signals of the selected values lat the lowand high frequen cies are received concurrently.

Another Iadvantage of the Iappamatus constituting this invention resultstrom the use of the antenna normally provided on an automobile toreceive radio signals as the antenna of transmitting signals to thereceiver at the garage door. This is accomplished by shortcircuiting theinput to the radio at the time that signals are to be transmitted to thereceiver at the :garage door. By slrort-circuiting the input to theradio, the limpedance of the nadio cannot be coupled to fthe antenna to`affect the tuning of the tnansmitted signals. Furthermore, the

v nadio cannot be damaged in :any Way in case of kany considerableintensity in the transmitted signals.

The apparatus constituting this invention |also has certain otheradvantages. It utilizes a simple mechanism to attach the transmitterunder the dashboard of lan auto mobile. This attachment is made in sucha Way that the transmitter can be easily lat-tached to the dashboard byfastening one screw land can be easily detached from the dashboard atany time by unliast-cning the screw.

In the drawings:

FIG. 1 is -a diagram of electrical circuitry showing the electricalconstruction of a transmitter included in one embodiment of theinvention;

FIG. 2 is la diagram of electrical circuitry showing the electricalconstruction of a receiver included with the transmitter shown in FIG. 1in one embodiment of the invention;

FIG. 3 is la tnagmentary perspective view of the housing for thetransmitter shown in FIG. 1 and illustrates the manner in which thetransmitter housing may be disposed under the dashboard 'of anautomobile;

FIG. 4 is an exploded perspective View of the different members formingthe transmitter housing shown in FIG. 3 fand illustrates how the variousmembems may be connected to one another and to the automobile dashboard;

FIG. 5 is a :fragmentary sectional view illustrating the constructionand relative disposition of a push butt-on shown in FIG. 4 and ofmembers associated with the push button including a pair of switchesincluded in the circuit diagram shown in FIG. 1;

FIG. 6 is a chant illustrating possible values lfor modulating signalsof low and high frequencies produced on a time-sfharing basis by thetransmitter shown in FIG. l;

FIG. 7 is a chant illustrating the possible combinations of modulatingsignals at the low and high f irequencics and [further illustrating thevalue of the capacitance which has to be added to obtain the desiredcombination of modulating frequencies; and y FIG. 8 is a schematicdiagram illustrating the diiferent possible connections between pairs ofterminals in a connector board shown in iFIG. l to .obtain theproduction of modulating signals at either high or low frequencies orthe production of modulating signals at both high and low frequencies ona time-sharing basis.

.connected to' the movable contact off the vibrator.

mounted in any suitable and convenient manner on an automobile to lsetndsignals toward a Agarage door. The antenna may be similar to those usedon automobiles at present to receive signals for operating the radios inthe automobiles. The antenna 10 may be used to receive signals ttorintroduction to the car radio during the time thaty it is not being usedto'obitain the opening or closing of a garage door. The connection tfromthe antenna 10 through a coil 11 tothe input to a radio (not shown) inan automobile is indicated schematically by a cable 12.

A pair of iganged single-pole single-throvv switches 14 e and 16 areincluded in the transmitter circuitry shown in cal1y-driven vibrator 18.The vibrator 18 may be of any suitable construction such as a type 1601manufactured by the P. R. Mallory Company. The vibrator 18 'is 'providedwith two stationary contacts which will hereafter be designated as theupper and lower stationary cont-acts to conform with the relativepositioning olf these contacts itn FIG. l. rPhe movable contact olf thevibrator 1S may b e spring loaded for normal disposition against thelower stationary contact of the vibrator in FIG. 1.

,'Ilhe upper `stationary Contact of the vibrator 18 is connected to oneterminal orf an energizing coil 20 included in the vibrator andthe otherterminal of the coil 20 is The upper stationary contact of the vibrator18 also has a common connection with one terminal of the primary windingin a transformer generally indicated at 22. The other :terminal of theprimary winding in the transformer '22 is connected to the middle one ofthree terminals in an adaptable terminal board generally indicated at24.

A resistance 26 having a suitable valuesuch as approximately 3 `ohms isconnected between the left and middleterminals ofthe bcand 24 and aresistance 28 having a suitable Vvalue such as approximately 13 ohms isconnected between the left and lright terminals of the board 24. Theleit yterminal of the board 24 is connected to one terminal kof abattery 25 in an automobile, the other terminal lor the batte-ry beinggrounded. Although the left terminal ofthe board 24 is shown as beingconnected to the positive terminal of the battery 25 in FIG.

l, it can also be connected'as electively to the negative terminal otthe battery. The right terminal of the board 24 is connected to firstterminals ccf the tilaments in the vacuum'tubes 'used `in thetransmitter, the second terminals orf the i-laments being lgfnounded.Actually, in the embodiment of the transmitter shown in FIG. l, only twotubes are included and both of these tubes may be disposed within asingle envelope.

i r[the terminal board 24 and the resistanoes 26 and 28 are included toadapt the transmitter shown in FIG. 1 for operati-on` in automobilesusing l6-volt batteries and in automobiles using `l2-vol-t batteriesVsince the new automobiles are now .using l2-volt batteries Whereas theold automobiles have been using 6-volt batteries. When the transmittershown in lFIG. l is to be enengized from a l2- volt battery, theconnections are made as shown in FIG. l and as described above. Foroperation of fthe transmitter shown in FIG. `1 ifrom a 6-volt battery,the three terminals in the board 24 are short-circuited to one another.

A rectifying stage :generally indicated at 32 is connected across thesecondary rwinding .of the transformer 22. Ilhe rectitying stage 32includes la capacitance 34 which is in parallel with the secondaryWinding tout the transformer 22 and which is provided with a suitablevalue such as approximately 0.01 microlfarad. One terminalof thecapacitance 34 is grounded and the other terminal :of the capacitance isconnected to the platterot a diode 36, which may be a itype lHWt12575',y mainteV factured bythe Siemens Company :off Germany.. The

cathode Voi? the diode 36 |has a comrnon connection with the iirstterminal of a capacitance 38, the second terminal of lwhich is grounded.The capacitance 38 mayV have a suitable value such as approximately 4microfarads.

The voltage fon the cathode of the diode 36 is applied to anintermediate tap in a. coil 40. The coil 40` is magnetically coupled tothe coil llfto induce signals' in the coil for introduction to theantenna 1%. A capacitance 42 having a suitable value such asapproximately Vl0 micromicr'ofarads is in parallel with thecoil 40l totune the coil to a particular carrier frequency.V The lower terminal ofthe capacitance 42 in FIGA is connected to a yfirst terminal in acrystal 44 which may be constnucted to provide a. suitable carrier(frequency suchV as approxi; mately 27.12 megacycles. This frequency isassigned by the .Federal Communications Commission. The frequency is thesame fior al-l manufacturers regardless of the number of manufacturiersand'rregardless of the nume ber of sets.

The other terminal of the crystal 44 is connected to the control gridoff a rtube 46. 'llhe tube 46 may be in-1 eluded with another tube in asingle envelope designated as a type 6AN8. When two tubes are includedin a single envelope, only one envelope is required in the transmitter,as will be'seen from the subsequent discussion..

A capacitance 45 is connected between the control grid lof the tube 46and' ground to neutralize any capacitive effects in the crystal `44.rBhe capacitance 45v may be provided with al suitable value such asapproximately l0 micromicrofarads. The control grid of the tube 46 isbiased by a pair of resistances 48 and 5G connected in series betweenthe control .grid and ground.. The resistances 4S and 50 arerespectively provided with suitable values such as approximately 10kilo-ohms and 22V kiloohr'ns. Y l

The plate of the tube 46 is connected to the upper tergrounded. Thescreen grid is positively biased from the cathode of the diode 36through a network formed byV a pair of resistance@` 52 and `55, whichare respectively provided kwith suitable values such as approximately 56kilo-ohms and 3.3 kilo-ohms. A capacitance 54 having a suitablevaluesuch as approximately 02001 microfarad is connected between the screengrid of the tube 46 and ground.

Signals are applied to the common terminal between the resistances 43and 50 through a suitable coupling capacitance 5 8 from the plate of atube 60 which may be included in a common envelope with the tube 46. Theplate of the tube 60` is adapted to receive a positive potential througha suitable resistancel 56 from the cathode of the diode 36. Theresistance 56 and the coupling capacp itance `58 may respectively havesuitable values such as approximately 6.8 kilo-ohms and 0.001micro'farad.r The cathode of the tube 60 has a common connectionwith oneterminal of a resistance 62, the other terminal of which is grounded.The resistance 62 may have a suitable value Lsuch as approximately 2.2kilo-ohms. cathode of the tube 60 also has a common terminal with anintermediate tap on a tuning coil 64.

A resistance 66 having a suitable value 'such as approximately l0kilo-ohms extends electrically between the grid of the tube 60 andground. A capacitance 68 is connected between the grid of the'tube 60and one end terminal of the tuning coil 64, rthe other end terminal ofthe tuning coil being grounded. A capacitance 70 having a suitable valuesuch as approximately 220 nn'cromicrofarads is in parallel with thetuning coil 64.

e A capacitance 72` and 'an adjustable tuning capacitance 76 have firstterminals connected to the ungrounded end terminal of the tuning coil 64and have lsecond terminals The connected to an intermediate terminal ina connector board 74. The combined value of the capacitances 72 and 76is dependent upon the frequencies to be provided for modulating signalsof relatively low frequency. The' combined value of the capacitances 72and 76 for different combinations of low and high frequencies may beseen from a chart `shown in F1GQ7. Variations in the.

combined value may be obtained by adjusting the capacitance 76 or byvarying the value of the capacitance 72.

The connector board 74 is provided with left, intermediate and rightterminals, and the left terminal is grounded. yTo obtain only modulatingsignals of relatively high frequency, none of the terminals in theconnector board 74 is connected to any of the other terminals in theboard. This may be seen from the schematic diagram shown in- FlG. 8i Thelett and intermediate terminals in the connector board are connectedtogether to obtain only modulating signals of relatively low frequency.For the production of modulating signals of both low and highfrequencies, the intermediate and night terminals in the board 74 areconnected together. The different electrical arrangements between theterminals in the board 74 are illustrated in FIG. 8. The dilerentcircuit arrangements produced by such connections will be described indetail subsequently.

The receiver shown in FG. 2 is located at the garage door and isdesigned to receive signals for opening or closing the door. connectedin a series circuit to ground with a coil 1012. A coil 104 ismagnetically coupled to the coil 102 Vand is in parallel with acapacitance 106 having a suitable value Y such as approximatelymicromicrofarads. First terminals ofthe coil 104 and the capacitance 106are grounded. A capacitance '108 and a resistance 110 are in lseriesacross the coil 104 and the capacitance 106. The capacitance 108 and theresistance 110 may be respectively provided with suitable values such asapproximately 100 micromicrofarads and 4.7 kilo-ohms.

The common terminal between the capacitance 108 and the resistance 110is connected to the control gnid of a tube 41112, the cathode andsuppressor grid of which are grounded. The tube 112 may be included withanother tube in an envelope designated asa -type 6X8. A capacitance 114having a suitable value such as approximately .01 microfarad isconnected between the screen grid of the tube 1.12 and the ground, Aresistance 1161s connected between the screen grid of the tube 112 and asource 123 of direct voltage to apply a limited potential of positivepolarity to the `screen grid. A capacitance 118 is connected between theresistance `116 and ground to decouple the positive potential from thesource 123 relative to ground. The resistance 1116 may have a suitablevalue such as approximately 56 kilo-ohms and the capacitance `118 mayhave a suitable value such as approximately 0.01 microfarad.

A tuned circuit is connected to the plate of the tube 112. The tunedcircuit includes a capacitance 120 having a suitable value such asapproximately l0 micromicrofarads and also includes the primary windingof a transformer 122. Second terminals of the capacitance 120 and theprimary Winding of the transformer 122 are connected to the positiveterminal of a source 123 of direct voltage to receive a suitablepotential such as approximately +140l volts.

The secondary winding ofthe transformer 122 has one terminal groundedand has the other terminal connected The receiver includes an antenna100 to the cathode of a diode A124, which may be a type a suitable valuesuch as approximately 10 megohms and is also connected to the grid of atube 132 which may be included in the same envelope as the itube 112.The cathode of the tube 132 is grounded and the plate of the tube isadapted to receive a positive potential.A This potential is applied fromthe same terminal of the voltage source 123 as the tuned circuit formedby the capacitance and the primary winding of the transformer 122. Thispotential is applied to the plate of the tube 132 through a resistance`1311 having a suitable value such as approximately 47 kilo-ohms.

A capacitance 136 is disposed electrically between Ithe plate for thetube 132 and ground. A capacitance 138 and a resistance are in seriesacross the capacitance 136. The capacitance 138 and the resistance 140may be provided with suitable valu-es such as app-noxiinately 0.101microfaradand approximately 1 megohrn. The common terminal between ,thecapacitance 138 -an-d the resistance 140 is connected to lthe controlgrid of a tube 142 which may be included with another tube in anenvelope designated as type 12AT7. The cath-ode of the Iturbe 142 isgrounded.

The plate or" the tube '142 is adapted to receive a posi- .tiv'epotential from lthe Same terminal of the voltage sou-nee 123 as theplate of the tube 132. This potential is applied to Ithe plate `of thetube 142 through a resistance 144 lhaving `a suitable value such a-sapproximately 47 kiloiohrns. A coupling capacitance 146 and laresistance 148 are in series `between the plate of the tube 142 andgnound. The capacitance 146 :and the `resistance 148 may be respectivelyprovided with suitable values such as 0.0101 microanad and 470kilo-ohms. The common lterminal between the capacitance 1416 and theresistance 148 is connected to the control grid of a tube 150 having,its cathode grounded.` The tube 150 may be included in fthe sameenvelope as the-tube 142.

Th same posit-ive potential is lapplied to the plate of the tube 150 asis applied to vthe plates of the tubes 132 and 142. This potential isapplied lthrough a resistance 152l having a Suitable value suchy as:approximately 47 kilo-ohms. One terminal of a coupling capacitance 154having -a suitable value Isuch as lapproximately 0.01 micnofai-ad isalso connected to the plate of the tube 150. The other terminal of thecapacitance 154 is connected to the plate of a diode 156 and to thecathode of ya diode 160. The diodes 156 land 160 may be included in atype IRC 9KR22 manufactured by the International Resistance Company. Thecathode of the diode 156 is grounded and the plate of the diode 160 isbiased at a suitable potential such Ias approximately -2 volts from thevoltage source 123. A capacitance 162 having a suitable value such asapproximately 0.01 microfarad extends electrical-ly from the plate orthe diode 1601to ground.

The second terminal of the capacitance 154 also has common connectionswith iirst terminals of oapacitances 166 and 168. A .tuned circuitformed by an adjustable coil 170 yand a capacitance 172 in parallel isconnected between the second terminal of the capacitance 166 and ground.Similarly, la tuned circuit formed by an adjustable coil 174 and -acapacitance 176 in parallel is connected between the second terminal :ofthe capacitance 168 and ground. The second terminals of thelcapacitances 166 and 168 are also respectively connected to lirstterminals of capacitances and 182, each of which is provided with lasuitable value such as approximately 0.001 microlfarad.

Second terminals of the capacitanees 180* and 182 are connected lto thecontrol grids of tubes 184' |and 186 which also respectively connectedto'frst terminals of a pair of capacitances 192 and 1.914, each having asuitable value such :as approximately 0.001 microtarad.

The second terminal tot the capacitance 192 has a common connection withthe cathode of a diode 1%, the plate of which is connected to thevoltage source 123 to receive a suitable negative potential such laslapproximately 7.5 volts. Resistances 19S, 1200 and 202 are in seriesbetween the control grid lof the tube 18,4 and the plate of thedifode196. The resistances 198, 200 `and 202 may be respectively provided withsuitable values such as 470 kilo-ohms, 100 kilo-.ohms and 2.2 megohms.llhe common terminal between `the resistanccs 200` and 202 is alsoconnected to the second terminal of the capacitan-ce 192. A capacitance204 having a suitable value such as 0.01 micnofarad is Iconnectedbetween the plate .of the diode 196 and they common terminalbetweenthe'resistances 198and 200.`

Similarly, the second .terminal of the capacitance 194 is connected tothe cathode of a diode `206, the plate of which is Iadapted to receivethe negative potential of approximately -7.S volts from the voltagesource 123. Resistances 208, 210 and 212 are in series between thecontnol grid of the tube 186 and the plate of the diode 206. Theresistances 2018, 210 `and 212 may be provided Y 214 having a suitablevalue such :as 0.01 microffanad is connected between the plate of thediode 206iy andy the common terminal between the resistances 208 `and210.

A relay coil 218 and 'a resistance 220 extend electrically in seriesfrom the common terminal between the resistvances 188 and 190 to theterminal in the voltage source 123 lior applying the positive potentialof approximately v +140 volts. The resistance 220 may be provided withla suitable value such as approximately 1.5 .kilodohms A capacitance 222having 'a suitable value such as approximately 50 microfarads is inparallel with the series branch formed by the relay 218 `and theresistance 220.

A switch 224 is magnetically coupled to the coil 218. the switch 224 maybe included in apparatus for obtaining the operation of a garage door toeither an opened position or `a closed position. For example, the switchmay be included-in apparatus disclosed and claimed in U.S. Patent2,805,059, issued September 13, 1957', to Willard I. Green. 'I'hisapparatus is illustrated schematically at 226 in FIG. 2. The lapparatusmay include a motor which is connected in a circuit with the switch `224to become energized upon Ithe 'closure of the switch.

' closed. When the switch. 14 is closed, it grounds the coil 11 and theungrounded terminal of the cable 12: to prevent radioy signals receivedby the antenna fnom being introduced to the radio (not shown) in anautomobile. Ihis multes the automobile radio so that power from thetransmitter shown in FIG. 1 cannot be introduced to the radio. This isdesirable to prevent the automobile radio Ifrom being damaged,especially when the power output from the tube 46 is not limited in amanner which will be described in detail subsequently. Furthermore, bygrounding the input to the automobile radio, the radio cannot-introduceany reactanceto the antenna 10 and the coil 11 to :affect the operationof the antenna and change the `frequency of response of the coil.

'l'lhe switch 16 becomes closed at the seme time as the switch 14. Thisgrounds the movable contact of fthe vibrator 18. Since the movablecontact of the vibrator 18 normally engages the lower stationary contactin FIG. l, a continuous circuit is established which includes theautomobile battery 25, the primary winding off the tnansformer 22, thecoil Ztl land the stationary and movable contacts of theswitch 1'6.rThis current causes the coil 2@ to become energized so as to actuatethe mov-able contact of the vibrator 18 into engagement with the upperstationary contact ofthe vibrator. In this position of the movablecontact of the vibrator 18, the ycoil 20 becomes short-circuited. Thiscauses the movable Contact of the vibrator to return to a positionengaging the lower stationary contact of the vibrator. ln'this way, themovable contact of the vibrator y1S alternates in engaging the upper andlower stationary contacts ofthe vibrator yat a frequency dependent uponthe characteristics of the spring loading of the movable contact.

Current ows through the primary winding of the transformer 22 whetherthe movable contact Yof the vibrator '1li is engaging the upper or lowerstationary contacts of the vibrator. However, in the lower position ofthe movable contact in the vibrator 18, the coil 2li is included in `aseries circuit with the primary winding of the transformer 22, whereasin the upper position of the 'movable' contact, the 'coil 20 is shortedout lof the circuit. This produces variations in the current flowingthrough the prirnary winding of the transformer 22. The current flowingthrough Itheprimary winding ,of the transformer 22 passes directlybetween the left 'and intermediate terminals of the connector board 24in FIG. 1 when the automobile battery is adapted to Vsupply 6 volts. Forthe cars employing 12-volt batteries', the current passes through theresistance 26 between the left and intermediate terminals of theconnector board 24. VIny this way, the system constituting thisinvention is easily adapted for use with both types of automobilebatteries Y included at present in automobiles.

VThe variations in the `current Flowing through the primary winding ofthe transformer 22 during alternate half cycles in thewoperationrotthevibrator 18 cause Ya Yvoltage 4to be induced in the secondary winding:of the transformer 122. The Voltage induced in fthe secondary windinghas an increased amplitude relative ,Ito the voltage `induced intheprimary because of the turns ratios in the windings. Y'lhe increasedvoltage in the secondary winding of the transformer 22 is rectiiied bythe stage formed by the capacitances 34 and 33 and the diode 316." 'I'hevoltage is introduced through suitable resistanccs to the screen gridlof the tube 6:6 and the plate of the tube 60 and is also introducedthrough the coil 40' to the plate of the tube 46.

When a positive potential is introduced :to the plate of the tube 60,current flows through the tube and the tuning coil 64. The coil 64 andthe capacitance 70 provide a tuning circuit resonant lat a relativelyhigh frequency constituting .la rst modulating frequency. This frequencyis seleotedon an individua-l basis for dilerent installations 'and isvariable in accordance with adjustments made in the tuning coil d4.' Asmay be seen in the chart shown in FIG. 6, at least seven `diierentmodulating frequencies of relatively high value may be provided byadjusting the tuning coil 6d. These frequencies may be selected in arange between 29` kilocycles per second and 52 kilocycles per second. Itshould be appreciated that both the range of the modulating signals atthe high frequencies and the numberof choicesin this range may beconsidered as arbitrary and that a different range and a differentnumber fof choices in the range may Y contacts of the switch 16, thelmovable and lower stationary contacts `of the vibrator 13, tand therighlt and intermediate terminals in the connector boand '74. Thiscircuit is established only during the time that the right andintermediate terminals in the connector board 74 are bridged by a leadto produce the operation designated as high and low frequencies in FIG.8. By grounding 9 the capacitances 72 and 76 in alternate half cycles,the capacitances 72 and 716 are placed in parallel with the capacitance70 to vary the resonant frequency lof the tuning circuit formed by lthecapacitances and @the tuning coil 64. v

The introduction of the capacitances 72'and 76 to the tuned circuitIformed by the coil 64 and the capacitance 70 causes the resonantfrequency of the tuned circuit to decrease. The amount of the decreasein :the resonant frequency is ldependent upon the values of thecapacitances 72 and 76 and can be varied by adjusting lthe value of theVcapacitance 76. By proper adjustments in this value, the resonantfrequency can be varied in increments between fa suitablerange such as9l kilocyclcs per second' and 35.5 'kilocycles per second. For example,at least nineincrements in range such as shown in FIGS. 6- and 7 can beobtained by proper adjustments in the value of the capacitance 76. Itshould be appreciated that this range and the number of choices in therange can also be considered as arbitrary and, therefore, can beiamendedwithout affecting the scope of the invention.

It will thus be seen that modul-ating signals of first and -secondfrequencies areproduced in the tube 69 on a timesharing basis. Inalternate half cycles of the vibrator 1S, signals of relatively highmodulating frequency yare produced, and in the other half cycles signalsof a relatively low modulating frequency -are produced. A considerablenumber of different combinations of relatively high and low modulatingfrequenciesy can be obtained by ladjusting the tuning coil 64 and thecapacitance 76.

As will be seen from the subsequent discussion, each installation at agarage is provided with fa `different comhination of low and highmodulating frequencies to distinguish the installation from all otherinstallations in the neighborhood. A Igarage door can be operated onlywhen the receiver at the door receives carrier signals modulated withboth low and high modulating frequencies of selected values. lIt shouldbe appreciated that the ranges of the low and high modulatingfrequencies tend to overlap somewhat. However, combinations -should Ibeprovided only where the high modulating frequency exceeds the lowmodulating frequency. This tends to restrict somewhat the number ofcombinations between the low and high modulating frequency, but asufiicient number of combinations are still available to provide .adistinction between different installations in ya neighborhood.

A possible number of different combinations of low and high modulatingfrequencies may be seen from the chart shown in FIG. 7. As will be seen,the combinations not considered desirable are indicated by an X in thechart shown in FIG. 7.l Nineteen possible combinations are designated byan X out of a total of 63 such possibilities so as to leave 44 actualpossibilities. The chart shown in FIG. 7 also indicates the value of thecapacitance 72'which has to be `added in microfar-ads in order to obtainthe selected frequency in the lo-w modulating range. As will be seen,the capacitance 72 would not have to be included `for -at least some `ofthe ac-tual combinations available.V It should be appreciated that theinclusion of the capacitance 72 only produces a rough approximation ofthe desired frequency `and that fine variations may have to be made byadjusting the capacitance 76 in order to obtain the desired frequency.

FIG. 8 illustrates the possible connections between the differentterminals in the connector board 24. For the production of both low andhigh frequencies on a timesharing basis -as set forth above, theintermediate and right terminals are connected together. When modulatingsignals 'at only the low frequency are desired, the left andintermediate terminals are connected together. This causes -a ground tobe constantly established to the capacitances 72 and 76 regardless ofthe positioning of the movable contact in the vibrator '18 such that thecapacitances are always included in the tuned circuit.

For the production of modulating signals` at only the high frequencies,no connections are made between the different terminals in the connectorboard 24. This prevents the capacitances 72 and 76 from being groundedregardless of the positioning of the movable Contact of the vibrator 1S.Since the capacitances 72 and 76 'are never grounded, the tuned circuitis constantly formed only by the coil `64 and the capacitance 70 toprovide modulating signals at the high frequencies. The connections tothe terminal board 74 for obtaining either signals of low modulatingfrequency or signals of high modulating frequency are provi-ded forcertain reasons. For example, an important reason is to facilitate thealignment of the receiver and the transmitter to the selected modulatingfrequencies so that the receiver will respond properly to thetransmitted signals. By testing for each modulating frequencyseparately, problems resulting from the production of harmonic signalsare considerably reduced. n

The modulating signals produced on the plate of the tube 60 yareintroduced to the control grid of the tube 46 through the couplingcapacitance S8 and the resistance 48. The tube 46 is included in amodified Colpitts type of oscillator. The oscillator also includes thecrystal 44 and the resonant circuit formed by the coil 40 Iand thecapacitance 42. This resonant circuit is tuned to substantially the same`frequency as the resonant frequency of the crystal 44. This frequencymay have a suitable value such as .approximately 27 i12 megacycles.However, it will be appreciated that any other suitable carrierfrequency can also be used. The frequency of the carrier signalsproduced by the modified Colpitts oscillator is designated for .allmanufacturers by the Federal Communications Commission. Since allmanufacturers Iare assigned the same carrier frequencies, it isimportant that a garage installation of one manufacturer should not beaffected by signals from transmitters installed in automobiles by othermanuy facturers.

The power output represented by the carrier signals from the tube 46 islimited in accor-dance with the requirements of the FederalCommunications Commission. This power input is ydesignated as milliwattsmaximum to the tube 46. The power limitation is obtained by limiting thepotential on the screen grid of the tube 46 to that approaching ground.The potential on the screen grid of the tube 46 is controlled by theaction of the network formed by the resistancesSS and 52. However, itshould be appreciated that 4an increased potentialcan be applied to thescreen grid of the tube 46y if no power limit-ations are imposed on thetransmitter by Agovernmental :authorities.

'Ihe carrier signals produced by the modified Colpitts oscillator aremodulated on a time-sharing basis with the :signals of vlow and highfrequencies produced on the plate of the tube `60. These signals areinduced from the coil 40 to the coil '11 so that they can be transmittedby the Vantenna 1f? to the antenna "10ft (FIG. 2) at the garage door.The signals received by the antenna 100 are introduced to the coil 102and are induced by that coil in the coil 104. The signals are thenintroduced to the control grid of the tube `1'1-2 to obtain anamplification of the signals in the stage which includes that tube.

AThe sign-als yfrom the radio frequency (RF) stage 'are introducedthrough the tnansformer 122 to the detector stage which includes thediode 124. rThe detector stage operates to demodulate the signals byeliminating the carrier frequency. The -output signals from the diode124 represent the modulating signals lat the low 'and high afrequencieson a time-sharing basis. These signals [are amplified -by lthe stageincluding the tube 132 yand fby the stages including the tubes 142 and15G.

The amplified signals from the tube 15d are lintroduced to the tunedcircuit formed 4by the coil 170 Iand the capacitance 172 :and to thetuned circuit formed by the coil 174 and the capacitance 176. Thecircuit formed by the coil and the capacitance 172 is tuned to the lowmodul-atingY frequency so as to pass signals only Kat that frequency.Similarly, the circuit formed by the coil 174' 'and the capacitance 176is tuned to pass signals only at the fhigh modulating frequency. ln thisWay, the tuned circuits act to channelize the modulating signals ofselected low and high frequencies into dilerent channels.

' The signals passed by the tuned circuits have amplitudes withinrelatively narrow limits because of the limit. ing action provided bythe diodes 160 land 156. For example, signals having ia positivelamplitude @above ground would pass through the diode 156 vto groundsuch that they would beunable to be presented to the tuned oir-V cuits.Similafrly, signals yhaving a negative amplitude greater than -2 voltswould be absorbed by the action of the diode 168 so as to be prevented.from being introduced to the tuned circuits. The action of the diodes156 Vand 160 in limiting the amplitudes of the signals introduced to thetuned circuit is important in obtaining the proper operation ofYsubsequent stages, as will become more apparent subsequently. Actually,the diodes 156 and 168 are biased-at a potential approximating -1 voltbecause of the iiow of leakage current through the diodes. The diodesthan act to limit any signal swing to an amplitudeof l volt on eitherside of the bias of -l volt.

The modulating signals passed by the coil -170 and the capacitance 172.r'are introduced through the coupling capacitance 180 to the control gridof the tube 184. These signals modulate the liow of current through 4acircuit including the power supply 123, the resistance 228, the coil218,V the resistance 188 and the tube 184. The lresultant amplifiedalternating voltage produced on the 'plate of the tube 184 is fed backthrough the capacitance V192 to the Vcathode of the diode 196 forrectilication by vproduction o-f an lamplified direct voltage areaccomplished in a single tube.vr This direct voltage causes a directcurrent to flow through the relay 218 and the resistance 220. Thecurrent flowing through the relay coil 218 has lan amplitude withinrelatively narrow limits because of the limiting action provided by theresistance '188. Y The tube 186 has a vcurrent 'iiow through it upon apassage of signals through the tuned circuit formed by the coil 174 andthe capacitance 176. The resonant signals produced on the plate of thetube 186 are introduced through the capacitance 194 to the 'cathode ofthe diode 286 to obtain a rectification of the signals. These rectiiedsignals are then smoothed by the capacitance 214 so that a correspondingpositive direct voltage is introduced to the control grid of the. tube186. In this way, a direct current flows through the relay coil 218 andthe tube 186 upon the introduction of an Ialternating signal to thecontrol grid of the tube. This current has an amplitude Withinrelatively narrow limits because of the limiting action provided by theresistance 190.

The relay coil 218 is provided with parameters so that it can actuatethe switch 224 only when current flows through both the tube 184 and thetube 186. In this Way, the rel-ay coil 218 can be operated only upon thereception at the receiver of modulating signals havingthe selectedvalues at the low range and at the high range. The relay coil 218 canIbe actuated only upon the receptionof modulating signals having therequired low and high frequencies since euch modulating signal isincapable of producing the required .magnetic force in the relay coil218. for actuating the switch 224. This results l2. #also results 'inpart from the 'action of the resistances 188 Iand 190. Y

The llimiting action provided "by the diodes 156 and Y, 160 isinstrumental in preventing Iany Iringing action in the tuned circuitformed by the coil and the-capacitance 172 or in the tuned circuitformed by the coil 174 land the capacitance 176. If ringing were tooccur in the tuned circuits, it would prolong the time of response ofthe circuits. This would tend to produce an actuation ofV resistances188 and 1901act` in this manner by limiting the 'Y llow of currentthrough the relay 218 at any instant. By limiting the flow of currentthroughthe relay 218 at any instant, the relay is able to `becomeenergized suiiciently only on la cumulative basis to actuate the switch224.

The capacitance 222 is included to provide a time delay for insuringthat the switch 224 will become actuated only upon the continuoustransmission of signals at the desired modulating frequencies from thetransmitter and not as a result of any random'varying generation ofsignals. The capacitance operates in this manner since it delays thebuild-np of any potential across the relay 218 for -a particular periodof'tim'e such asiat least 1 second. Y

The apparatus disclosed above has certain importantV advantages. It isable to provide a discrimination between a multitude of differentinstallations in a neigh-` borhood even though the receivers at thediierent installations may all receive carrier signals at the samefrequency. This results from the use of diierent cornbinations ofmodul-ating signals at low and high frequencies. For example, 44diivferent combinations of modulating patterns can be obtained whenseven possible modulating frequencies are made available in the low`range and nine possible modulating frequencies are made available in thehigh range. This may be seen from the chart shown in rFIG. 7.Correspondingly increased numbers of combinations may be made availableby increasing the number of choices in the low and high modulatingranges. By providing these different combinations, a clear-cutdiscrimination between differentV installations is obtained so that onlythe garage door at the desired installation becomes operated Theapparatus constituting thisrinvcntion has certain' other importantadvantages. IFor example, the circuitry at the transmitter for producingthe modulating signals at the low and high frequencies is relativelysimple. This results from the production of the modulating signals at vthe two frequencies on a time-sharing basis. By producing the signals ona time-sharing basis, the same tuned circuit can be `used to produceeach frequency but addi-Y tional reactance is inserted into the circuitperiodically to change from one of the modulating frequenciesrto theother.

Additional advantages are also obtained from theparticular constructionof the transmitter. I'his results from the use of a single integral pushbutton for obtaining the operation of the system constituting theinvention. When depressed, this push button causes the radio receiver inan automobile to Vbecome shorted laga-inst the reception of any signals.At the same time, kor preferably slightly thereafter, the depression ofthe' switch causes power to be introduced to the stages Vfor producingthe carrier signals and the modulating signals. This sequence ofoperations prevents the radio receiver'in the automobile from beingdamaged by any signals radiated by the antenna when 'signals are beingtransmitted toward the receiver at the garage door. 1t also prevents anyreactance 13 from being introduced to the antenna and the coil 1 -1 fromthe input to the automobile radio so as to affect the operation of thesemembers. lIt also prevents signals from being produced or from beingradiated toward a garage door installation except during the time thatthe push button is positively actuated.

The circuitry at the transmitter is also advantageous to the operationof the receiver. This results from the fact that the signals at each ofthe two modulating frequencies are produced at the transmitter on `atime-sharing basis v and consequently are introduced to the receiver atseparate times. This avoids the production of beat frequency signals andharmonics which would other-wise be produced if signals at the twomodulating frequencies were introduced to the receiver at the sametime.` Since the signals at the two modulating frequencies areintroduced to the receiver on a time-sharing basis, they can be easilyand simply separated by the use of two resonant circuits tuned to theproper frequencies.

The receiver is also advantageous for another important reason. Itprovides a very convenient circuit for converting the alternatingsignals passing through the tuned circuits into a proportionate directvoltage. This direct voltage is Vampliiied in the same circuit as thatwhich receives the alternating voltage from the tuned circuits. Thecircuit is vso constructed that a relay in the circuit can becomesuliiciently energized to actuate a switch only when modulating signalsat the selected frequenies are able to pass through both of the tunedcircuits. By converting in one stage the alternating signals into aproportionate direct voltage and using the direct voltage to controllthe operation of a relay, increased accunac-ies and sensi-tivities inthe operation of the' relay are obtained and without any increase in thenumber of required stages.

'The apparatus constituting this invention has certain other importantadvantages. This results from the packaging of the transmitter shown inlPIG. 1 and from the construction of the housing and the attachment ofthe housing to the dashboard of an automobile. As will be seen in FIG.3, the transmitter is adapted to be attached to the dashboard 300 of anautomobile at a position preferably under the dashboard and preferablydirectly beneath a radio 302 in the automobile.

The housing for the transmitter includes a first casing generallyindicated at 304 in FIG. 4. The casing 304 is provided with a top wall306, a pair of spaced side walls f 308 and a rear Iwa-ll 310. Pairs ofholes 312 are provided in the top wall 306 at spaced positions in thelongitudinal direction. The holes -312 in each pair are preferablydisposed near the side walls 3018 to provide a iirm engagement betweenthe casing 304 and the dashboard 300. This engagement is obtained byscrews 314 which pass through any selected holes and into the dashboard300;

A stud 318 extends downwardly from the top wall 306 of the casing 304 ata position intermediate the side walls 308 and toward the front of thecasing. The stud 31'8 is internally threaded to receive a fiat-headedscrew 32d extending upwardly through la hole (not shown) in a casinggenerally indicated at 3120. The casing 320 is provided 'with a bottomwall 322 and a front wall 312,4

(1F-1G. 5) to form an enclosed housing .with the casing 304. The casing320 is also reinforced by a -p-air of upwardly turned lateral flanges325 (FIG. 4) which become disposed lwithin the side 'walls 3013 of thecasing 304. The bottom Wall 322 of the casing 320` is adapted to Vreston a flange portion 326 extending horizontally inwardly from the rearwall 310 of the casing 304.

A name plate 328 is easily attachable to the front Wall '324 of thecasing 320 as by tabs (not shown). Since the name plate 3218 is themember primarily visible to the riders in the automobile, it can beprovided with the name of the manufacturer and can be provided with apleasing appearance. A push button 330 (IFIGS. 4 and Y ld- 5) extendsthrough holes in the front wall3$4 and in the name plate 328. The pushbutton 330 is coupled to the switches `14 and 'le in FIG. l to obtain aclosure of the switches l:upon a depression of the push button and isspring-loaded as at 332 to maintain the switches in the normally openedposition.

The casing 304 is initially attached to the dashboard 300 as by thescrews 314. The casing 320 is thereafter attached to the casing 304 asby the nat-headed screw 321. Since the casing 320 carries all of theelectrical components forming the transmitter shown in FIG. l, thetransmitter can be easily removed from the dashboard 300 for any desiredadjustment or repair merely by removing the Screw 321. A cable (notshown) leading to the (radio (not shown) is included in the transmitterand is supported by the casing 320. The cable extends to the radiothrough an opening 334 in the rear wall 310 of the leasing 304. Anothercable also extends through the opening 334 to the antenna 10.

The apparatus described above is primarily adapted for use to provide aremote control over the operation of a garage door. It should beappreciated, however, that the apparatus constituting this invention isalso adapted for other uses. For example, the transmitter can bedisposed within a house and the receiver can be disposed in anautomobile to obtain an automatic starting of the automobile a fewminutes before the driver is ready to leave the house. vIn this way, theautomobile engine can become fully warmed on winter days at the timethat the driver is ready to leave.

The apparatus constituting this invention has been described primarilyin connection with the production of modulating signals having low andhigh modulating frequencies. It should be appreciated that themodulations can be obtained in other ways than by differences infrequencies. For example, modulating signals having rst and secondcharacteristics can be produced by shifting the signals in phase toprovide the signals with iirst and second distinctive phases.

It should be appreciated that semiconductors such as transistors can beused in place of the vacuum tubes shown in FIGS. 1 and 2 and describedabove. The reason for this is that both semiconductors and vacuum tubesserve as Icurrent control members.

Although this invention has been disclosed and illustrated withreference to particular applications, the principles involved aresusceptible of numerous other applications which will be apparent topersons skilled in the art. The invention is, therefore, to be limitedonly 4as indicated by the scope of the appended claims.

1. In combination for controlling the operation of a garage door from aremoved position in an automobile: an antenna connected in theautomobile normally to receive radio signals for the reception of audioprograms in the automobile; first switching means coupled to the antennaand operative to short circuit the input to the radio; second switchingmeans coupled to the rst switching means for actuation with the firstswitching means; means coupled to the second switching means andoperat-ive upon the actuation of the switching means to produce carriersignals at a lirst particular frequency and including means'coupled tothe antenna for obtaining a transmission of the signals by the antenna;means coupled to the second switching means and operative upon theactuation of the switching means to produce modulating signals at asecond particular frequency for modulating the carrier signals; means atthe garage door for receiving the carrier signals; means coupled to thereceiving means for demodulating the received signals to obtain only themodulating signals; and means coupled to the demodulating means forobtaining an operation of the garage door mechanism only upon theoccurrence of modulating signals of the second particular frequency.`

arcaeri 2. In combination for controlling the operation of a garage door`from a removed position intantautomoble: an antenna connected inthe-automobile normally to receive radio signals for the reception of audioprograms in the automobile; means including a first tuned circuit forproducing carriersignalsV and including a coil magnetically coupled tothe antenna for introducing signals to the antenna for transmission tothe garage door; means including a second tuned circuit for producingmodulat- Ying signalsv at a particular frequency and coupled to theresponsive to modulating signals at the particular fre-Y quency forobtaining an operation of the garage door.

3. In combination for controlling theoperation of a garage door from aremoved position in an automobile: an antenna connectedin the automobilenormallyfto receive radio signals for .the reception of aud-io programsin the automobile; means including a first tuned 'circuit for producingcarrier signals and including a coil magnetically coupled'to the antennafor introducing signals to the antenna for transmission to the garagedoor', a second tuned circuit resonant at a first particular modulatingfrequency and coupled to the first tuned circuit for providing amodulation of the carrier signals; means including reactance meansdisposed electrically for kcoupling to the tuned circuit and adjustableto produce a resonance in the circuit at a second particular modulatingfrequency; means including a first switclh operative upon actuation toshort circuit the input to the radio; means including a second switchganged to the first switch and operative upon actuation to introduce apotential to the first and second tuned circuits for obtaining theproduction of carried'and modulating signals; means coupled to thesecond switch and operativey upon actuation of the circuit to obtainresonance of the ,tuned circuit at a Y second modulating frequency; anantenna for receiving signals; switching means coupled to the antennafor inhibiting the reception of signals by theantenna upon the operationof the switching means; means operatively coupled to the reactancemeansand the tunedY circuitV and to the switching means for establishingthe connections between the reactance means and the tuned circuit andfor disestablishing such connectionsl on a time-sharing basis upon theoperation ofthe switching means to produce modulating signalsalternately at the rst frequency and at the second frequency; meansoperatively coupled to the antenna and the last mentioned means forproviding carrier signals ata third selected frequency and second switchto alternately obtain a coupling of the re- Y ternately obtain theproduction of signals at the first and second modulating frequencies;means at the garage for modulating the carrier signals with the signalsalter- Vnately produced at the first and second frequencies to producesignals for transmission to the distant mechanism and for introducing'such .modula'tedvsignals to the antenna for transmission by the antennato the removedV position; means at the distant mechanism for receivingthe transmitted signals; means coupled to the receiving means forseparately demodulating the received signals .Y

to introduce modulating signals only at the first frequency to a tirstchannel and to introduce modulating signals only at the second frequencyto a second channel; and

means coupled to the demodulating means and responsive only to themodulating signals of both the first andV second frequencies on thetime-sharing basis for produc'- ing an output signal for operating thedistant mechanism. 6. In combination for controlling the operation of adistant mechanism from a removed position by obtaining the transmissionof signals from an antenna normally adapted to rece-ive radio signals;first switching means cluding tuned electrical circuitry and includingsecondV switching means responsive to the actuation of the firstswitching means for alternately varying the characteristics of the tunedelectrical circuitry to modulate the carrier signals with signals of afirst selected frequency at first particular periods of time and formodulating the carrier signals with signals of a second selectedfrequency door for receiving the transmitted signals; means operai tiveupon the-received signals for detecting the received signals to passonly the modulating signals; means coup'led to the detecting means andincluding-a first circuit resonant to pass modulating signals only ofthe first particular frequency and including a second circuit resonantto pass modulating signals only ofthe second particular frequency; andmeans responsive only to modulating signals of both the first and secondparticular frequencies to obtain operation of the garage door.

4. The combination set forth in claim 3, in which the door-operatingmeans includes a pair of stages each coupled to a different one of theresonant circuits to receive modulating signals of a different one ofthe two selected frequencies and each constructed to amplify 'themodulating signals and including unidirectional means to convert theamplified alternating signals into a proportionate direct current and inwhich the door-operating means includes means coupled to thelast-mentioned stagesffor operation only upon the concurrent fiow of adirect current through both of the stages.

5. In combination for controlling the operation of a distant mechanismfrom a removed position: a tuned different from the first frequency atsecond particular periods -alternating with the first particularperiods; means responsive to the lmodulated carrier signals fortransmitting the modulated carrier signals toward the distant mechanism;means at the distant mechanism for receiving the transmitted signals;detecting means operative upon thereceived signals to pass only themodulating signals; means including tuned electrical Ycircuitryresponsive to the modulating signals for separately passing the firstmodulatingy signals of the first selected frequency and theV secondmodulating signals of the second -selected frequency; means includingrst detecting means responsive to the first modulating signals toproduce a first detected signal and including second detecting meansresponsive to the second modulating signals to produce a second detectedsignal and including means coupled to the first and second detectingmeans for producing an output signal only upon the sequential productionof the first and second detected signals; and means responsive to theoutput signalsfor obtaining an operation of the distant mechanism.

7. In combination for controlling the operation of a distant mechanismfrom a removed position by obtaining the transmission of signals to theremovedV position by an antenna normally adapted' to receive radiosignals:` a capacitance; means including a first tuned circuit and firstswitching means for alternately coupling the capacitance into thecircuit and isolating the capacitance from'the circuit upon alternateoperations of the firstswitching means to produce modulating signalshaving first and second particular `frequencies on a particulartime-sharing basis; means including a second tuned circuit for providingcarrier signals and coupled to the first tuned circuit and tothe antennafor modulation of 4the carrie-r signals ;by the modulating signalshaving the first and second particular frequencies and for transmissionof the modulated carrie-r signals-by the antenna tothe distantmechanism; second switching means operatively coupled to the antenna-forpreventing the reception of signals by the antenna upon the actuationofthe second switching means and operatively coupled to the firstswitching means for obtaining the alternate operation -of :therstswitching means upon the actuation of the second switching means;receiving means at the distant mechanism; detecting means 4coupled tothe receiving means for extracting the modulating signals; first meanscoupled tothe detecting means and resonant at the first modulatingfrequency for p-assing onlyA the -first modulating signals; second meanscoupled to the detecting means land resonant at the second modulatingfrequency for passing -only Athe second modulating signals; firstdetecting means coupled to the first resonant means for converting thefirst modulating signals into a first direct voltage related to theamplitude of the signals; second detecting means coupled to the secondresonant means for converting the second modulating signals into asecond direct voltage related to the amplitude of the signals; vmeanscoupled to the lfirst and second detecting means and responsive only tothe cumulative effect of the first and second direct voltages forproducing an output signal; and Vmeans responsive to the output signalfor obtaining an operation of the distant mechanism.

8. In combination for controlling the operation of a distantmechanismfrorn a removed position by obtaining the transmission ofsignals to theremoved position by an antenna normally adapted to receiveradio signals: a tuned circuit resonant at avfirst particular frequency;switching means operatively coupled tothe antenna forpreventing thereception of signals rby the antenna upon the actu-ation of theswitching means; resonant means including a capacitance disposedelectrically for coupling to the tuned circuit and adjustable to producea resonance in the circuit at a second particular frequency; secondswitching means operative at a particular repetition rate and responsiveto the actuation of the first switching means to connect the capacitanceinto the tuned circuit and to disconnectthe capacitance from the circuiton a time-sharing basis related to the particular repetition rate;-means for providing carrier signals at a third particular frequencyandV operatively coupled to the :resonant means for obtaining amodulation of the carrier signals with the signals at the first andsecond frequencies |and operatively coupled to the antenna for obtaininga transmission of the modulated carrier signals by the antenna to thedistant mechanisrn upon the actuation of the switching means; means atthe distant mechanism for receiving the transmitted signals; meanscoupled to the receiving means `for demodulating the received signals toproduce modulating signals alternately at the first frequency and at thesecond frequency; and means coupled to the demodulating means forproducing an operation of the distant mechanism only upon the alternatepassage of modulating signals at the first and second :frequenciesthrough the demodulating means at the particular repetition rate.

9. In combination for controlling the operation of a garage door from aremoved position in an automobile and for simultaneously preventing theVreception of, radio signals by an antenna on the automobile: meansoperatively coupled to the antenna for providing carrier signals at aselected frequency and for introducing the carrier signals tothe'fantenna for transmission by the Vantenna toward the garage door;switching means operatively coupled to the antenna for preventing thereception of signals by the antenna upon the actuation of the switch-M18 ing means; means operative upon the carrier signals and responsiveto the actuation of the switching means for modulating the vcarriersignalswith 4alternating signals of a particular frequency; means at thegarage door for receiving the modulated carrier signals; meansresponsive to the modulated carrier signals :for detecting the modulatedcarrier signals to pass onlythe modulating signals; a

stage responsive to the modulating signals from the detecting means andincluding a current control member for amplifying the signals andincluding unidirectional means for rectifying the signals from thecurrent control memfber and-including a capacitance for smoothing therectified voltage into a direct voltage and including impedance meansforfeeding the direct voltage to the current control member forfurtheramplification by the current control member of the direct voltage; andmeans including a relay responsive to the flow of Idirect currentthrough the cur- -rent control mem-ber to obtain the operation of thegarage door.

l0. In combination for controlling Athe operation of a 4garage door froma removed position in an automobile and for simultaneously preventingthe reception of signals 4by an antenna on the automobile: switchingmeans operatively coupledto the antenna for preventing the reception ofsignals -by lthe antenna upon the actuation of the switch- 4ing means;means including electrical circuitry responsive to the `actuation of theswitching means for providing .modulating signals of a selected lowfrequency and modulating signals of a selected high frequency on atimesharing basis; means including electr-ical circuitry opera-'tivelycoupled to the antenna and the last mentioned means forVproviding carrier signals of a third selected frequency Jandformodulating the carrier signals with the modulating signals of theselected low and high modulating frequencies and for introducing -themodulated signals to the antenna -for transmission by the antenna towardthe garage door; means including electrical circuitry at the garage doorfor receiving the transmitted signals; means including electricalcircuitry coupled to the receiving lmeans yfor detecting the receivedsignals; means including first resonant circuitry responsive to themodulating signals of the selected low frequency and including second lresonant circuitry responsive to the modulating signals of the selectedhigh frequency for separately passing the signals of the selectedfrequencies; a first electrical stage responsive to the modulatingsignals of the selected high modulating frequency from the resonantmeans and including first current control means for amplifying thesignals and including first undirectional means for rectifying theamplified signals from the current control means and including a firstcapacitance for smoothing the rectified voltage from theunidirectionalmeans into a direct voltage and including first impedance means forintroducing the `direct voltage from the first capacitance to thecurrent control mea-ns for amplification of the direct voltage; a secondelectrical stage responsive to -the modulating signals of the selectedlow modulating frequency from the resonant means and including secondcurrent control means for amplifying the s-ignals and including secondunidirectional means for rectifying the amplified signals from thesecond current control means and including a second capacitance forsmoothing the rectified voltage from the unidirectional voltage into adirect voltage and including second impedance means Afor introducing thedirect voltage lfrom the second capacitance to the current control meansfor amplification of the direct voltage; means including a relayresponsive to the current through Ithe first and second current controlmeans to become energized only upon a concurrent flow of current throughthese means; and means responsive -to the relay when energized to obtainan operation of `the garage door. Y

l1. In combination for controlling -the operation of a Igarage door froma removed position in an automobile and for preventing the reception ofsignals -by an antenna on the automobile: switching means operativelycoupled the antenna upon an actuation of the switching means; meansincluding a tuned coil and a rst capacitance connected across the coilfor providing modulating signals haying a selected high frequency; meansincluding a second capacitance electrically connected to become coupledto the tuned coil and the first capacitance for providing modulatingsignals having a selected low frequency; means including a vibratoroperatively coupled to the switching means for producing an alternatevcoupling of. the second capacitance to the first capacitance and thetuned coil and an alternate de-coupling of the second capacitance fromthe tuned coil and the first capacitance upon an actuation oftheswitching means; means including a tuned circuit for producing carriersignals and for modulating the signals with the modulating signals oflow and high frequencies and for introducing the modulated signals to'the antenna for transmission by the antenna toward the gara-ge door;means at the garage door for receiving the transmittedrsignals; meanscoupled to the receiving means for detecting the received signals topass only the modulating signals; means responsive to the signals fromthe deringing in the resonant means; and means coupled to the first andsecond resonant means and responsive only upon the concurrentintroduction of the modulating signals of the selectedlow and highfrequencies to provide anoperation of the garage door.

12. The combination set forth` in claim 11, in which: the door-operatingmeans includes a first stage for receiv- Ving the modulatingsignals oflimited amplitude and of the selected low frequency and in which thefirst stage includes a first current control member for amplifying thesesignals and in which the first stage includesfirst means for rectifyingand smoothing lthe amplified modulating signals from Vthe first currentcontrol member into a `direct vol-tage and in which the first stage alsoincludes first means for introducing vthe direct volta-geffro'm the rstrectifying and smoothing means to the first current control member andin which the first stage includesV first means for limiting the currentthrough the first current control member; and in Which'thedoor-operating` means includes a second stage for receiving themodulating signals of ylimited amplitude and of the selected highfrequency and in which the second stage includes a second currentcontrol member for'arnplifying these signals and in which t'ne secondstage includes second means for rectifying and smoothing the amplifiedmodulating signals` from the second current control member into adirectV Voltage and in which the second stage also includes second means:for introducting the direct voltage from -the second rectifying andsmoothing means to the second current control 'member and in which thesecond stage includes sec References Cited in the file of this patentUNITED STATES PATENTS y 1,654,927 Farrington Ian. 3, 1928V 2,500,212Starr Mar. 14, 1950 2,522,893 Purington Sept. 19, 1950 2,565,540Williams Aug. 28, 1951 p 2,662,109 Tapp et al. Dec. 8, 1953 2,675,544Trimble Apr. 13, 1954 2,699,301 Clute Jan. 11, 1955 2,705,321 Beck et alMan/29, 1955 2,724,074 Welker Nov. 15, 1955 2,788,521 Undy Apr. 9, 19572,841,700 Handen July 1 195s 2,847,497 Appleton et al. Aug. 12, 19582,931,956 van Andale Apr. 5, 1960 FOREIGN PATENTS 125,838 Australia Oct.21, 1947

1. IN COMBINATION FOR CONTROLLING THE OPERATION OF A GARAGE DOOR FROM AREMOVED POSITION IN AN AUTOMOBILE: AN ANTENNA CONNECTED IN THEAUTOMOBILE NORMALLY TO RECEIVE RADIO SIGNALS FOR THE RECEPTION OF AUDIOPROGRAMS IN THE AUTOMOBILE; FIRST SWITCHING MEANS COUPLED TO THE ANTENNAAND OPERATIVE TO SHORT CIRCUIT THE INPUT TO THE RADIO; SECOND SWITCHINGMEANS COUPLED TO THE FIRST SWITCHING MEANS FOR ACTUATION WITH THE FIRSTSWITCHING MEANS; MEANS COUPLED TO THE SECOND SWITCHING MEANS ANDOPERATIVE UPON THE ACTUATION OF THE SWITCHING MEANS TO PRODUCE CARRIERSIGNALS AT A FIRST PARTICULAR FREQUENCY AND INCLUDING MEANS COUPLED TOTHE ANTENNA FOR OBTAINING A TRANSMISSION OF THE SIGNALS BY THE ANTENNA;MEANS COUPLED TO THE SECOND SWITCHING MEANS AND OPERATIVE UPON THEACTUA-